The present invention relates to a tape cassette, and is particularly concerned with a video tape cassette for uses such as for 8 mm video tape recording.
A tape cassette shown in FIGS. 5 to 7 (detailed in Japanese Utility Model Application Laid-Open No.118180/1984) is known for use such as 8 mm video tape recording. These figures show the lower half case 1 of this cassette where a magnetic tape 4 passes between a pair of tape reels 2 and 3 through the front of the cassette. In this front, a front cover 110 (actually installed in the upper half case but not shown in the figure). The rear part of the cassette is constructed to keep the tape reels 2 and 3 at a stop while they are not in operation in a way that they may be locked by engaging the reel locking pawls 6 and 7 with the teeth 8 and 9 provided at the periphery of the flange of the tape reels letting the flat upper surface 5a of a reel lock 5 slide on the upper half case inner surface.
FIGS. 6, 7(A) and 7(B) each show the reel lock 5 and its surroundings. FIG. 6 is a cross section taken on line VI--VI of FIG. 5, and FIGS. 7(A) and 7(B) each a cross section taken on line VII--VII of FIG. 5.
The reel lock 5 is installed so that it may slide along a guide ribs 16 in a level in the front or rear direction in the cassette. On its front, the above-mentioned reel locking pawls 6 and 7 are mounted projectingly, and between its rear side and the back side of the lower half 1, a compression spring 10 is provided. Therefore, the reel lock 5 is constantly pressed toward the front of the cassette, and the locking pawl 7 engages with the tape reel teeth 9. When locking is released, a release pin 11 as shown by the hypothetical line in FIG. 6 is inserted through a hole 12 to hit a slant face 13. As a result of this, the lock 5 is forcedly moved to the right direction of the figure (towards the rear of the cassette), pressing the spring 10, and the locking pawl 7 disengages from the tooth 9. Incidentally, the numeral 14 denotes the upper half case of the cassette, and 18 a label glued to the back side of the cassette.
In this mechanism of reel locking, to prevent the lock 5 from rising, that is, slipping upward, the lock 5 is retained by keeping the flat upper surface 5a of the lock on the retaining rib 15 located on the upper half case 14. In an example shown in FIG. 7(A) of the mechanism, one such retaining rib is provided, while another example shown in FIG. 7(B) has two.
On account of the above, it has been necessary with the conventional cassette to mold the retaining rib 15 as part of the upper half case 14, and this causes what is called a sink mark to come up on the front surface of the upper half case 14, leading to an impairment of the appearance of the cassette and a lowering of its commercial value.
On the other hand, the inventor of the present invention has improved the above tape cassette and made this improvement public in Japanese Utility Model Application Laid-Open No. 177479/1989. FIG. 8(A) shows a reel lock 25 which has a height that its upper surface 25a may reach the inner surface 14a of the upper half case 14. Since the upper surface 25a of the reel lock 25 contacts with the inner surface 14a of the upper half case, this improved tape cassette prevents the reel lock 25 from slipping upward and so ensures stopping the rotation of the tape reels or releasing such locking. The elimination of the above-mentioned rib or ribs 15, resulting in flatness in and around the above-noted area with which the reel lock upper side is in contact, prevents sink marks from coming out and impairing the appearance after molding of the upper half case 14, thus implementing a good appearance and enhancing the commodity value.
In the course of further examination and analysis of this improvement, it has been found that the tape cassette still has a problem to cope with. Because the lock 25 in this tape cassette is made so that its upper surface is flat to be in slidable contacting with the inner surface 14a of the upper half case 14, the lock 25 tends to be too large and heavy and has a high center of gravity which causes it to be unstable in movement.
It is therefore the chief object of the present invention to provide a tape cassette whose reel lock is light weight and small with the lower center of gravity so that the lock may be easy to assemble into the cases and ensure smooth movement to the inner surface of the upper half case which has no sink mark on the molded outer surface.
Now, the background of the present invention in relation to another object of the invention will be described.
FIGS. 18 to 22 (detailed in Japanese Patent Application Laid-Open No. 18268/1988) shows a prior art video tape cassette for use such as 8 mm video tape recording.
The case 101 of this tape cassette is made up of upper and lower cases (halves) 1a and 1b, and has a tape reel 103, located both right and left inside the case, for winding a magnetic tape 102. The tape reels 103 are upon the right and left holes 105 for insertion of driving shafts, and are pressed downward by a leaf spring 107 whose one end is fixed on the inner surface of the upper part 106 of the case 101.
To a case 101, a front lid 110 is attached rotatably for opening and closing the front of the case to protect tape. This front lid 110 has a front plate 111 for covering the entire front of the case 111, support plates (side part of the front plate) 112 provided at both the right and left ends of the front plate 111 extending to the back of the case and pivots 113 protruded from the supports 112 to face each other. The pivots 113 are inserted in the holes 116 formed in the front ends 115a of the right and left sides 115 of the case 101 (as shown in FIG. 20). The front lid 110 rotatably changes the position to open the front of the case 101 or to close it and vice versa, but a torsion spring 117 provided to a pivot 113 applies its force constantly to the lid so that it may rotate and return to the closing position usually. When the tape cassette is not in use, the front lid 110 is closed and locked to protect that part of the magnetic tape 102 which is guided to the front of the case. There is a space 121 between the right front side wall 115a of the case and the right side support plate 112 of the lid to face each other (this space may be provided at the left side), and in the space 121 a means 156 for locking the front lid 110 when it is closed is installed. When a tape cassette has been set into a video tape recorder, the locking releaser 141 provided to the recorder moves, in the direction and course shown by the arrows 165, into the space 121 from the front side of the case 101, reaches and pushes the locking means 156 and therefore releases the locking of the front lid 110. As a result, the front lid 110 opens, and the tape loading pin of the video tape recorder comes into the pocket 119 in the front of the case 101 to bring the tape 102 toward the front of the case. Now, in FIG. 20, a slant face 123 having step is formed on the outer surface of the front end 115a of the right side wall 115 of the case, as is located at the halfway of the wall 115. Thus, the above-mentioned space 121 is wider at its front half 121a than at its rear half 121b, as the slant face comes to its boundary. More concretely, the slant face 123 with step is formed over the total length of the upper and lower cases and is closer to the front of the case than the above-mentioned pivot hole 116. And side space, the front edge of the front end 115a is processed to form curved edge to make a guiding slant face 125 causing the space to widen toward the front of the case. The protruding base 113a of the pivot 113 protruded from the right support plate 112 of the front lid 110 is contacted with the outer side of the front end 115a to ensure a constant width at the narrower rear half 121b.
In this narrower half 121b of the space 121, the rotatable locking equipment is installed which is the means 156 for locking the front lid 110 when it is closed.
In FIGS. 20 to 22, the locking equipment 156 is composed of an arm 157 one end of which is a fulcrum 170 for rotation, a hook 160 for engaging, another arm 162 connected to the arm 157 and its part 161 for being pushed (to release locking) which is formed at its lower edge. The side wall of the space 121 which is closest to the rear of the case has the opening 163 for the insertion of a leaf spring 164 to make a match contact between the side wall 132 of the lower case 101b and the side wall 133 of the upper case 101a, and the leaf spring 164 inserted into the opening 163 presses the locking equipment 156 so that the equipment 156 turns clockwise. The locking equipment 156 is to be mounted on the lower case 101b before the fixing of the upper case 101a and this lower case are put together. Concerning the torsion spring 117, the coil 117a in its middle is installed on the above-mentioned pivot 113, one end 117b of the spring is placed in and supported by a longitudinal groove 139 provided for the outer surface of the front end 115 of the right side wall 115 of the case, and the other end 117c is laid and supported on the spring shoe 140 provided on the inner surface of the right support plate 112 of the front lid 110.
Thus, when the tape cassette is not in use, the engaging hook 160 at one end of the locking equipment engages upward with the part 167 of the front lid 110 in the closed position to securely lock the front lid 110 and prevent it from turning on the pivot 113 and opening upward. When the tape cassette with the front lid closed is inserted, the locking releaser 141 is introduced into the space 121 through a front opening 142 at the front lid 110 part and pushes the front of the part 161 of the locking equipment 156 which is to be pushed. Then, the locking equipment 156 turns anticlockwise as shown by the hypothetical line in FIG. 21, the leaf spring 164 being distorted, the hook 160 disengages from the part 167 of the front lid and then the locking of the closed front lid is released. Here, the locking equipment 156 under the presence of the above-mentioned curved guiding edge 125 and of the slant face 123 with step works effectively according as the locking releaser 141 is guided in the space 121 and correctly pushes the part 161 of the locking equipment 156 even if a cassette was loaded with a little malpositioning into a video tape recorder.
Incidentally, both the right and the left lower part of the front plate 111 of the front lid 110, where the part the tape is pulled out to the front of the case 101, as shown in FIGS. 18 and 21, are cut to make the openings 142, and projections 143 from the front edge of the bottom plate 104 of the case are formed so that the top 144 of the projections may be located in a position corresponding to the middle of the thickness of the front plate 111.
The above-mentioned tape cassette, however, has the following disadvantage in the locking equipment. The locking equipment 156 rotates round the fulcrum 170. But this fulcrum 170, as shown in FIG. 22, is placed from above in a pair of grooves 171 formed in the lower case 1b. But since it is not fastened in this position, it must be prevented from slipping out the grooves 171 by putting the upper case 1a and the lower case b together, that is, holding the fulcrum with the lower surface 101c of the upper case 101a. Therefore, in the process of assembling the tape cassette, since the locking equipment with the fulcrum 170 simply placed from above in the lower case 101b easily slips out the position by contingencies such as vibrations, a lot of care needs to be taken in this assembly process, that will lead to lower productivity.
It is therefore another object of the present invention to provide a tape cassette so constructed as to retain its lock equipment stably so that it may lead to efficient and steady assembly of the tape cassette.